Project Summary States have responded to the current opiate crisis through implementing several different types of policies, such as prescription drug monitoring programs (PDMPs), expanded naloxone access, and Good Samaritan immunity. At present, the full efficacy of each of these policies is unknown beyond examinations of a limited set of policies, localities, or years. This research study will use causal statistical methods and a robust policy database to examine the impact of relevant policies on opiate use, dependence, and fatal overdose from 1999 to the present. For policy data, we will employ the new and as yet underutilized NIDA-funded Prescription Drug Abuse Policy System (PDAPS) to evaluate the effects of opiate relevant policies. We will accomplish this goal by coding this database by state and year and combining it with mortality data from the Center of Disease Control and data on use and dependence from the National Survey on Drug Use and Health, as well as time- varying control measures from the U.S. Census Bureau and FBI Uniform Crime Reports. We will analyze this dataset using fixed effects and difference-in-difference models, which are causal methods for observational data well-known for the elimination of unobserved heterogeneity, such that estimators are robust to any observable or unobservable time-invariant omitted variables. The fixed effects and difference-in-difference approaches respectively provide a causal interpretation of (a) whether a given state experiences a decrease in opiate outcomes after passing a particular policy, and (b) whether a state that passes a policy experiences a decrease in opiate outcomes relative to a state that does not have that policy. The PDAPS database contains detailed policy information (e.g. to whom practitioners can prescribe naloxone, who has access to PDMPs), such that we can determine which of the nuanced approaches to these policies are most efficacious. We will examine whether each policy component affects use, dependence, and fatal overdose for opiates generally as well as separately for prescription opiates and heroin. In addition, we will test for synergistic effects of policy; that is, whether the combination of any given policies is particularly effective. Finally, we will conduct these analyses by key demographics: gender, race/ethnicity, age, and urbanicity, which will permit the identification of related health disparities. Our proposed exploratory research provides an opportunity to test the impact of a rapidly evolving policy landscape on opiate outcomes and will contribute in additional ways. First, if certain policies or combinations of policies are identified as efficacious, the results would provide evidence for broader adoption to curb the current opiate crisis. Second, the identification of possible health disparities in the benefits of policy implementation may not only help public health professionals to work towards redressing these disparities, but also identify policies that may ?bypass? social inequalities to provide comprehensive benefits to citizens. Finally, this exploratory study establishes a foundation for future research that will consider local policy variation, individual-level policy-driven changes, and non-fatal overdose.